Sometimes we need to scale-down and up daemonset for debugging or any other purposes. Natively Kubernetes does not allow to do it via standard method using kubectl due to design of DaemonSet itself
What is DaemonSet in Kubernetes 🔗
Official Kubernetes documentation says: A DaemonSet ensures that all (or some) Nodes run a copy of a Pod. As nodes are added to the cluster, Pods are added to them. As nodes are removed from the cluster, those Pods are garbage collected. Deleting a DaemonSet will clean up the Pods it created.
So if simplify in Kubernetes, a DaemonSet is a special type of workload that ensures a copy of a specific Pod runs on all (or selected) nodes in the cluster, which leads to conclusion that for deployment of DaemonSet workload we need to set selector where such workload should be deployed. This means that if we will put dummy nodeSelector for daemonset which does not exists our DaemonSet will be scaled-down do 0, because there is no nodes with selector which is not exists
Managing scale manually of DaemonSet in Kubernetes 🔗
Based on the definition of DaemonSet, we can get straight-forward understand that we need manage of nodeSelector and put dummy value for it, so we can do something like that:
kubectl patch daemonset <{daemonset-name}> -p '{"spec": {"template": {"spec": {"nodeSelector": {"dummy-selector-non-exists": "true"}}}}}'
with defining namespace you can use --namespace (-n) flag:
kubectl -n <{namespace-name}> patch daemonset <{daemonset-name}> -p '{"spec": {"template": {"spec": {"nodeSelector": {"dummy-selector-non-exists": "true"}}}}}'
where:
<{daemonset-name}>- DaemonSet name what we want to scale to 0<{namespace-name}>- namespace name where DaemonSet located
But when we scaling DaemonSet to 0, how we can make opposite operation and scale it back? Answer is simple - dummy nodeSelector should be removed.
kubectl patch daemonset <{daemonset-name}> --type json -p='[{"op": "remove", "path": "/spec/template/spec/nodeSelector/dummy-selector-non-exists"}]'
with defining namespace you can use --namespace (-n) flag:
kubectl -n <{namespace-name}> patch daemonset <{daemonset-name}> --type json -p='[{"op": "remove", "path": "/spec/template/spec/nodeSelector/dummy-selector-non-exists"}]'